Layers of epitaxial cerium oxide have been found to be excellent buffer or intermediate layers for high temperature superconducting thin films as described by Wu et al. in Appl. Phys. Lett. 58 (19), 2165 (1991). Other related metal oxides have since been found to behave in a similar fashion to the cerium oxide. An interesting result of the use of these metal oxide buffer layers is that the crystal structure of the metal oxide buffer layer can match the crystal structure of the underlying substrate or can have a crystal structure rotated by 45.degree. from the basal plane with respect to the crystal structure of the underlying substrate depending upon the particular material selected as the underlying material.
Others have taken advantage of this crystal structure effect to form junction devices such as superconducting quantum interference devices (SQUIDs) wherein such a device includes a base substrate of strontium-titanium oxide, a patterned interlayer of magnesium oxide upon the surface of the substrate whereby an intermediate article with an exposed surface of both the patterned interlayer of magnesium oxide and the base substrate is formed, a coating of cerium oxide as a buffer layer over the entire exposed surface of the intermediate article, and, a ceramic superconductive material layer as an overcoat upon the buffer layer whereby the ceramic superconductive material situated directly above the substrate without the underlying patterned interlayer has an in-plane orientation of crystal structure different than the ceramic superconductive material situated directly above the patterned magnesium oxide interlayer. Unfortunately, when cerium oxide is directly deposited upon magnesium oxide, the result is a mixture of in-plane orientations thereby diminishing the junction performance. Also, magnesium oxide is very hygroscopic making manufacture more difficult.
Accordingly, an object of this invention is to provide a superconductive article such as a junction device having both a first region and a second region, said first and second regions each having an in-plane orientation of crystal structure distinct from the other region, said article eliminating the direct contact between magnesium oxide and a cerium oxide buffer layer of the prior art.